I was wondering whether there are any uranium deposits in the ocean floor, or in the rock walls of the continental shelf, etc.

I was hoping to have some deep sea uranium deposits accessible from the water, for fiction writing. So I would like to know if such has ever been found, or if it's possible to have uranium deposits so near to the ocean.

$\begingroup$Was this answer not good enough?$\endgroup$
– kingledionOct 26 '16 at 16:04

$\begingroup$I thought Uranium ions were mobile in water - unlike Thorium. This transition then being used in geochemistry. (it is over 20yrs since I took a geochemistry class!)$\endgroup$
– winwaedOct 26 '16 at 18:29

$\begingroup$@gerrit Yes, but spread out so thin it isn't useful for my purposes. I need a Uranium deposit.$\endgroup$
– J. DoeOct 26 '16 at 20:29

$\begingroup$@kingledion Oh, I didn't see the edit. Didn't know you checked the Earth Science stack exchange (neat). There was nothing wrong with the answers there, I merely wanted more information about mining deposits.$\endgroup$
– J. DoeOct 26 '16 at 20:31

3 Answers
3

There is no reason you couldn't have uranium deposits in the continental shelf. Certain types of deposits wouldn't occur or be likely to persist in that environment but other types such as those in Archean metasediments likely could be found.

As pure speculation, I can envision formation of deposits similar to unconformity or roll-front deposits where deep-circulating groundwater discharges through organic-rich ocean sediments. The organic material would cause the uranium to precipitate in a reduced oxidation state. That would likely be up on the shelf so I don't know if you could make it work if you want to be down on the edge of the shelf.

$\begingroup$I would have to disagree with Haresfur on this. The vast majority of continental shelf environments are way to oxygenated for uranium to be deposited. The only exception would be anoxic basins like the Black Sea. However there is no significant source of uranium around the black Sea. Uranium deposits in the Archaen metasediments exist only because the Earth's atmosphere was almost totally anoxic during that era.$\endgroup$
– Gordon StangerOct 28 '16 at 7:21

There are about 3 tonnes of uranium in every cubic kilometre of seawater, but in the general circulation there is no mechanism to concentrate the uranium, except perhaps low-level adsorption on manganese nodules in some parts of the sea bed. To concentrate the uranium you need some mechanism to transport it, and some other mechanism to make it precipitate. Both are pH-redox controlled, requiring substantial reducing conditions. The nearest plausible mechanism I can think of is a high concentration of uranium in groundwater, such as in the Aktau province of Kazakhstan, adjacent to the Caspian Sea. At present the Caspian is too oxygenated, and is likely to remain that way because of inflow from the Volga, but if climate change alters the rainfall-runoff relationship then that inflow to the Caspian would be reduced. Conceivably, it wouldn't take too much more pollution and reduced river inflow to make the deeper parts of the northern Caspian more reducing. Then maybe you could get uranium deposition at the groundwater-lakewater interface.

Old, AKA existing, deposits on the continental shelf are certainly possible and are an active target of the shelf mineral surveys in a number of countries but most current oceanic basins are too well oxygenated at depth for current deposits to be building up.